Battery electrode inspection system

ABSTRACT

The present invention relates to a method for inspection of a multilayer electrode sheet for a battery cell, comprising at least the following steps: joining together at least two functional layers; connecting the functional layers to form an electrode-separator assembly; detecting at least part of a surface of the electrode-separator assembly by means of a detection device for generating a measurement result; evaluating the generated measurement result and generating an evaluation result; and outputting the evaluation result.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from German Patent Application No. 102020 104 668.5, filed Feb. 21, 2020, which is incorporated by referencein its entirety.

FIELD OF THE INVENTION

The present invention relates to a method for inspection of a multilayerelectrode-separator assembly for a battery cell and to a device forinspection of the electrode-separator assembly and a battery cell.

BACKGROUND OF THE INVENTION

Lithium-ion batteries are increasingly seen as a key technology inmodern technology. Therefore, they are subject to continuous furtherdevelopment of different aspects, such as production costs, achievableenergy density, service life, safety and/or charging time, to name onlya few examples.

Batteries for storing larger amounts of energy, such as tractionbatteries in vehicles, generally consist of a plurality of batterycells, which in turn are composed of a plurality of cell components.Cell components of battery cells are electrodes, separator layers,current collector layers or current collectors, layers of activematerial on the electrodes, electrolytes and surrounding housings orfoils.

The lithium-ion batteries or the battery cells constructed according tothis principle basically have two electrodes. On the one hand, there isa negative electrode called the anode and, on the other hand, a positiveelectrode called the cathode.

The electrodes usually consist of current collectors and activematerial. In each case an active material appropriate for the polarityis arranged on the electrode sheet. A different active material is usedon the anode than on the cathode. At least one separator layer, whichprevents an electrical short circuit between the electrodes, is alsoprovided between two electrodes of different polarity. At the same time,however, the separator layer is permeable to certain ions, such aslithium ions, so that these ions can pass through the separator layerwhile the battery is being charged or discharged.

For the battery cells to function, an ion-conducting electrolyte is alsorequired, which wets the active layers of the electrodes and theseparator layer in such a way that it acts as a mediator for theprocesses in the cell. The terms anode and cathode are defined using theoxidation or reduction process. Which of the two electrodes is oxidizedor reduced depends on whether the battery cells are being charged ordischarged. When considering batteries or battery cells, however, it hasbecome common practice to always use the discharge process as adefinition for the terms anode and cathode.

The negative electrode of the battery cells often consists of a copperfoil and a layer of graphite or lithium-alloyed material as theelectrochemical active material. The positively charged lithium ionsrequired for the provision of power are stored in the negative electrodeduring charging (intercalation). Graphite anodes are currently the mostcommon choice because they have a low electrode potential and a lowvolume expansion during the storage of lithium ions. The positiveelectrode often consists of mixed oxides that are applied to an aluminumcollector. The positive electrode with the active material assigned toit serves as a lithium source during charging of the cell.

Known lithium-ion batteries are generally composed of a large number ofelectrode sheets which are arranged one above the other in a batterycell. In the production of battery cells, it is therefore advantageousfirst of all to interconnect a plurality of the required layers havingthe desired layer structure to form electrode sheets in order then toproduce battery cells, also called cell stacks, from the prefabricatedelectrode sheets in a further manufacturing step.

For example, during a lamination process, individual components of thebattery cells, such as the anode, the separator layer and the cathode,are firmly connected to one another so that their position andorientation are fixed relative to one another. This creates a so-calledmultilayer electrode sheet, which is referred to below as anelectrode-separator assembly (ESA). Particularly in the case oflarge-format battery cells, such as so-called pouch cells, lamination isan advantageous method both to increase the process speed in themanufacturing process and to improve the cell performance in the laterend product. The invention is not necessarily limited to a monocellassembly (anode, separator, cathode, separator); it can also be used forindividual laminated electrode sheets (e.g. separator, anode,separator).

However, the lamination process is a very complex production process.Extremely sensitive materials have to be processed. The processing ofseparator layers is particularly critical because they are extremelysensitive to the pressure and temperature loads prevailing in theprocess. The challenge during the process is to achieve an optimalconnection between the layered cell components without confirming thecell components.

All previously known methods for connecting the layers require arelatively complex process management. Random checks must be carried outregularly to ensure that the various layers have been reliably connectedto one another.

The solutions known up to now, therefore, have the disadvantage thatthey are complex and are suitable only to a limited extent forlarge-scale manufacture. In addition, defective production processes canremain undetected for a relatively long time until the next sample istaken and evaluated.

SUMMARY OF THE INVENTION

The object of the present invention is therefore to at least partiallysolve the problems arising from the prior art. In particular, a methodfor inspection of laminated electrode-separator assemblies and batterieswith electrode-separator assemblies is specified which is suitable forlarge-scale manufacture and ensures inspection of the safe and reliableconnection of the layers to one another.

To achieve these objects, methods and devices with the featuresaccording to the independent claims are proposed. Advantageous furtherdevelopments are the subject matter of the dependent claims. Thefeatures listed individually in the claims can be combined with oneanother in a technologically sensible manner and can be supplemented byexplanatory facts from the description and/or details from the figures,further embodiment variants of the invention being shown.

The proposed method for inspection of a multilayer electrode-separatorassembly for a battery cell comprises at least the following steps:

a) joining together at least two functional layers;b) connecting the functional layers to form a multilayerelectrode-separator assembly;c) detecting at least part of a surface of the electrode-separatorassembly by means of a detection device for generating a measurementresult;d) evaluating the generated measurement result and generating anevaluation result;e) outputting the evaluation results (in particular for manual ormachine processing).

The method designed in this way enables seamless and timely processmonitoring of the production process.

For this purpose, in a first step a), at least two functional layers caninitially be arranged relative to one another, wherein a predeterminedpositioning and orientation of the two functional layers is maintained.

“Functional layers” in this context are cell components that arenecessary for the battery cell to function, such as layered orplate-shaped cathodes, anodes and separators.

“Joining together” is understood here in particular to mean how thefunctional layers are joined relative to one another. The functionallayers should overlap one another and should be correctly oriented withrespect to one another in order to be (permanently) connected to oneanother in this position.

The “orientation” of the functional layers relates to the use offunctional layers that have a specific orientation direction. Theorientation can optionally be the alignment along, for example, thewidth, length or height of the functional layer. Thus, for example, itis possible to use functional layers of which the strength/resilience ishigher in a first direction than in a second direction transversethereto. Furthermore, functional layers can also be used which areoriented in the direction of the height of the functional layer. Forexample, layered electrodes can be used which are specially prepared onone side for contact with a corresponding active material. Theseelectrodes should then be arranged so that they are oriented in such away that this prepared surface comes into contact with the associatedactive material during the joining together.

In the following or subsequent step b), the functional layers thuspositioned with respect to one another are connected to form anelectrode-separator assembly.

An “electrode-separator assembly” can thus be understood as a“permanent” assembly of at least some of the functional layers joinedtogether in step a). The assembly takes place in particular over a largearea over the length and width of the relevant functional layer. Theelectrode-separator assembly can optionally be produced from functionallayers of a predetermined length or from endless strips of functionallayers which are joined and connected to one another with the desiredlayer structure. When endless strip-shaped functional layers are used,endless electrode-separator assemblies can be produced from which themultilayer electrode sheets or electrode-separator assemblies with adefined length can then be manufactured by cutting to length.Alternatively, the functional layers can first be individually cut tothe desired length and can then be connected to one another.

Afterwards or subsequently, in a step c) for quality assurance, theconnection created between the functional layers is checked. For thispurpose, at least part of the surface of the electrode-separatorassembly is first detected by means of a detection device in order togenerate a measurement result from it.

A “surface” is understood here to mean one (of the two) outer surface(s)of the electrode-separator assembly which is oriented parallel to thejoining plane or parallel to the functional layers. A substantial partof the surface is preferably covered, for example with an area in therange from 1 to 1000 cm² or from 1 to 100% of the surface in contact.

The “detection device” is particularly suitable for detecting thesurface topography, surface temperature and/or surface color. This cantake place by means of an optical sensor, a photographic apparatusand/or a camera.

It is possible for the “detection device” to comprise at least onelighting unit which can emit light onto the surface of theelectrode-separator assembly to be detected.

The detection device can generate and pass on electronic data and/orelectrical signals as a measurement result. The measurement result canbe (temporarily) saved or passed on directly.

This measurement result is then evaluated in the subsequent step d) inorder to generate an evaluation result therefrom.

The “evaluation” can include a comparison, a change, and an analysis ofthe measurement result on the basis of predetermined characteristicvalues, functions and/or calculation routines. This can includeprocessing of the electronic data and/or electrical signals. It is alsopossible to include image processing and/or image analysis. Theevaluation result can be (temporarily) saved or passed on directly.

This evaluation result is then output in the final step e) in order tobe further processed.

In particular, the evaluation result is transferred to a higher-levelcontrol unit or display unit (outside the detection device). The outputis preferably carried out in such a way that it can result directly orautomatically in a display and/or an adaptation of the productionprocess.

Steps c) to e) make it possible to continuously monitor the productionprocess and to produce consistently high quality through the immediatereal-time detection of defective electrode-separator assemblies. In thiscontext, real-time detection means that defective electrode-separatorassemblies are detected within only a few milliseconds and that thecorresponding evaluation results can be immediately initiated toeliminate the defect. These measures can consist, for example, inidentifying the defective electrode-separator assemblies as defectiveand removing them from the production process. Another measure canconsist in changing the parameters selected in the selected connectionprocess of the functional layers in step b). If, for example, laminationis used in the connection process, the pressure and/or temperature canbe adjusted as parameters.

In particular, it is proposed for further development that at least oneelectrode is joined together with an active material layer and at leastone separator layer in step a). Here, the electrode consists, forexample, of an electrically conductive substrate and a layer of activematerial applied thereto. In an advantageous development of theinvention, it may also be provided that the electrode is firstmanufactured individually or simultaneously during the manufacture ofthe electrode-separator assembly by connecting at least one substratelayer and one active material layer as functional layers.

Another development may for example provide that an anode and a cathodeand two separators are connected to one another at the same time in oneproduction step. This would correspond to a four-layer structure of theelectrode-separator assembly.

In principle, it is possible to produce the electrode-separator assemblyin the most varied configurations. For example, the electrode-separatorassembly can have a two-layer, three-layer or multilayer structure. Inaddition, a current collector, as a so-called collector tab, can also beincluded or laminated directly as part of the layer structure of thefunctional layers.

Electrode collectors are provided to protrude from the cell stack inorder in this way to deliver the generated current to an electricalconsumer located outside the cell stack. Inside, electrodes are providedto conduct a generated current directly or via current collectors to therespective associated electrode collectors of the same polarity. Copperfoils which are in contact with a graphite coating which has a lowelectrode potential can be used, for example, on the anode side as thesubstrate foil. On the cathode side, the substrate foils can bedesigned, for example, as aluminum collectors to which a mixed oxide isapplied. The graphite anode can be used as the first active material andthe mixed oxide can be used as the second active material. If a largenumber of electrode sheets are now arranged within a battery cell, thebattery cell can have a positive and a negative electrode collector andthe other electrode-separator assemblies can be connected to therelevant positive or negative electrode collector via collector tabs. Inthe case of a multilayer structure of the electrode-separator assembly,corresponding separator layers are to be provided which reliably preventelectrical contact between the electrode-separator assemblies ofdifferent polarity.

In particular, it is advantageous if the functional layers are connectedto one another (over a large area) by means of a lamination process,adhesive process or welding process. These processes can be implementedextremely cost-effectively and reliably in industrial large-scalemanufacture. The lamination process, in particular, can be preciselytailored to the respective requirements via the parameters of time,pressure and temperature.

It is particularly advantageous if steps a) to e) are carried out oneafter the other in a continuous process. This allows the advantages ofthe high manufacturing speed of continuous manufacture to be combinedwith continuous supply of the functional layers and continuous qualitymonitoring. Continuous within the meaning of the invention includes bothcontinuous processes of feeding the functional layers with a constantfeeding speed, and also those continuous processes in which thefunctional layers or sections of functional layers are fed with aconstant cycle rate. The same applies to the removal speed or cycle rateof the removal of the inspected finished electrode-separator assemblies.In particular, prefabricated electrode-separator assemblies can also befed to the inspection, in which case the step of connecting thefunctional layers can be omitted.

Immediately after the functional layers have been connected, thedetection device can detect at least part of the surface of themanufactured electrode-separator assembly and can then generate ameasurement result which can be evaluated by machine and which generatesan evaluation result during this evaluation. This evaluation result isthen output continuously, so that a human operator or a connectedautomated machine control can carry out an action to eliminate defectsin accordance with the evaluation result.

As soon as the evaluation result indicates, for example, that theconnection of the functional layers to one another no longer meets thepredetermined requirements, production can be stopped and the defectivesections of the electrode-separator assembly can be removed. As alreadymentioned above, this can be done manually by an operator or can beperformed automatically by a machine control. Depending on the selecteddetection device, the surface of the electrode-separator assemblyproduced can be detected completely, i.e. on both sides, or onlypartially, i.e., for example, on one side. In addition to the one-sideddetection of the surface of the electrode-separator assembly, it ispossible that only certain partial areas of the electrode-separatorassembly are detected by the detection device. In certain applications,it may be sufficient to monitor partial areas of the electrode-separatorassembly during the detection, instead of the entire area or the entirewidth of the electrode-separator assembly.

In particular, it may be provided that the surface is detected by meansof an optical camera system. With a camera system, it is particularlyeasy to monitor one side of the manufactured electrode-separatorassembly if the camera system is stationary and the electrode-separatorassembly is moved through the detection area of the camera system in acontinuous process. As an alternative to the imaging method using acamera system, the detection can be carried out with other systems, suchas systems that work with visible or invisible light, radar, laser orultrasound, in order to check the quality of the connection between thefunctional layers.

It is particularly advantageous if the evaluation of the measurementresult is carried out by means of an electronic data processing systemwhich is configured for image processing, preferably for gray scalevalue determination and/or creation of a gray scale value histogram.Such a data processing system can, for example, evaluate the measurementresult generated by the camera system. In the case of a camera system,the measurement results are individual images or a continuously changingsequence of images that are passed on to the data processing system forevaluation. Within the data processing system, the evaluation takesplace according to predetermined rules.

In particular, it is provided that an associated characteristic valueand in particular a gray scale value is determined when the measurementresult is evaluated. This ACTUAL characteristic value is then comparedwith a predetermined TARGET characteristic value in the context ofevaluating the measurement result, the evaluation result beingdetermined by comparing the ACTUAL characteristic value and the TARGETcharacteristic value. For this purpose, it may be specified, forexample, that an ACTUAL characteristic value that is greater than orequal to a predetermined TARGET characteristic value is accepted, whilean ACTUAL characteristic value that is less than the predefined TARGETcharacteristic value is not accepted. If the ACTUAL characteristic valueis not accepted, the considered section of the electrode-separatorassembly does not meet the quality requirements.

It has proven to be particularly advantageous if the measurement resultprovided (by the camera system) is subjected to an evaluation of thegray scale values. It can be observed that there is a correlationbetween the gray scale value of the surface of the electrode-separatorassembly and the quality of the connection between the functionallayers. In principle, this correlation can be written in such a way thatthe better the adhesive bond is between the functional layers, thehigher the gray scale value of the measurement result generated by thecamera system will be. In turn, the higher the gray scale value is, thedarker the gray shades will be on the corresponding measurement resultor image of the detection system. However, there is a maximum abovewhich there is no longer any increase in adhesive strength. From thispoint on, there is even a decrease in adhesive strength. The gray scalevalue formation of the recorded images is carried out with an imageprocessing program. A gray scale value histogram is created, whichindicates how many pixels in an image have a certain gray scale value. Amean value is then formed from these values, which is used to comparethe samples. From the recorded image of the camera system, with the aidof the function an area is selected that is to be integrated into thegray scale value formation. As a result, the gray scale value is notonly determined locally, but a large-area integral is determined, fromwhich the mean value is then formed. It should be noted here that thedetermined gray scale values only represent relative gray scale values.To determine the exact gray scale values, the image processing systemused can be calibrated beforehand with a gray scale.

In order to obtain measurement results that are as constant as possible,it is advantageous if step c) is carried out under constant and definedlighting conditions. This can be achieved, for example, by illuminatingthe area of the electrode-separator assembly to be detected with anartificial light source and shielding it from the influence of externallight sources, such as daylight, for example by a shield. For thispurpose, the camera system is ideally arranged together with a lightingunit within a housing. In this way, the reliability of the evaluationresult can be significantly increased.

The object is also achieved by a device for inspection of a multilayerelectrode-separator assembly for a battery cell, which is equipped witha feed device for at least two functional layers for anelectrode-separator assembly, wherein a detection device for detectingat least part of the surface of the electrode-separator assembly isprovided, which generates a measurement result corresponding to thedetection and which has an evaluation device for evaluating themeasurement result, which device outputs an evaluation result after theevaluation has taken place.

The device is set up in particular to carry out the method proposedhere.

In particular, a device with at least one detection device and means isproposed, these being suitable for carrying out the steps a) to d)explained here. Furthermore, a computer program [product] is proposed,comprising commands which cause this device to carry out the steps a) tod). A computer-readable medium is also proposed on which this computerprogram [product] is stored.

By means of the device designed in this way, the inspection of themanufactured electrode-separator assembly can be carried outcontinuously and at high speeds, wherein complete process monitoring inreal time, a so-called in-line inspection, is implemented.

This makes it possible to significantly increase productivity, sinceinterruptions for quality assurance and for carrying out measurementsare no longer necessary. At the same time, the reject rate can besignificantly reduced, since defective connections between thefunctional layers are recognized immediately and briefly aftermanufacture has taken place. If defects occur in the connections in theelectrode-separator assembly, only extremely small lengths of defectiveelectrode-separator assemblies are produced before a user or a machinecontrol can stop the system or take measures to eliminate the faultafter the evaluation result has been output.

The present invention also proposes a battery cell, in particular alithium-ion cell, which has at least two electrodes each having at leastone electrode-separator assembly. The electrode-separator assemblies ofthe different electrodes have an at least two-layer structure, areproduced according to the claimed method and are separated from oneanother by at least one separator layer. The battery cell produced andobtained in this way is particularly cost-effective to manufacture andhas excellent electrical properties.

As a precaution, it should be noted that the numerals used here(“first,” “second,” . . . ) serve primarily (only) to differentiatebetween a plurality of similar objects, sizes or processes, and inparticular, therefore, do not necessarily prescribe any dependencyand/or sequence of these objects, sizes or processes relative to oneanother. Should a dependency and/or sequence be necessary, this isexplicitly stated here or it is evident for the person skilled in theart to study the specifically described configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and the technical environment are explained in more detailbelow with reference to the accompanying figures. It should be pointedout that the invention is not intended to be limited by the exemplaryembodiments mentioned. In particular, unless explicitly statedotherwise, it is also possible to extract partial aspects of the factsexplained in the figures and to combine them with other components andfindings from the present description. In particular, it should bepointed out that the figures and in particular the proportions shown areonly schematic. in which:

FIG. 1: is a schematic representation of a device for inspection of anelectrode-separator assembly;

FIG. 2: is an embodiment of the proposed method from lamination to grayscale value determination;

FIG. 3: is a diagram with the correlation of gray scale value andadhesive strength; and

FIG. 4: shows a motor vehicle with battery cells according to thepresent invention;

In FIG. 1, a device 1 for performing the method explained here is shownin a schematic side view.

DETAILED DESCRIPTION OF THE INVENTION

By means of a feed device 2, an already laminated electrode-separatorassembly 3 is fed in from the left.

In the embodiment shown, the electrode-separator assembly 3 has anelectrode 4 and two separator layers 5. Active material layers 6 arealso located between the electrode 4 and the separator layers 5. In thestate shown, the functional layers 7 consisting of the electrode 4 withthe active material layers 6 and the two separator layers 5 are alreadyconnected to one another by lamination. The lamination joins theelectrode 4 and the active materials 6 located thereon to the separator5. The process steps a) and b) of the process have already been carriedout.

In the next step, at least part of the surface of the laminatedelectrode-separator assembly 3 is detected. For this purpose, theelectrode-separator assembly 3 is moved into a housing 8. The housing 8shields the electrode-separator assembly 3 located therein from externallight influences. In order to achieve constant lighting conditionswithin the housing 8, a dedicated lighting system 9 is provided therein,which illuminates the electrode-separator assembly 3 optimally and in aconstant manner.

In the embodiment shown, a surface 10 of the electrode-separatorassembly 3 is recorded by means of a camera system 11. In other words,only a partial area of the surface 10 of the electrode-separatorassembly 3 is detected, namely the upper side, while the lower side isnot detected. Alternatively or additionally, the electrode-separatorassembly could also be examined and inspected on the lower side throughan opening (window) in the conveyor system or an inverted vacuum belt.The measurement result captured by the camera system 11 is passed on inthe form of an image via a signal line 12 to an electronic dataprocessing device 13.

Alternatively, the inspection can also be carried out by continuouslytransmitting images and measured values in a rapid time sequence and canprovide a measurement result in the form of a measured value sequence orvideo sequence.

Image processing then takes place in the data processing device 13 inthe form of a gray scale value determination. In the determination ofthe gray scale value, a gray scale value is determined for the imageprovided by the camera system 11. This gray scale value can bedetermined for the entire image or for parts of the image. After atleast one gray scale value has been determined, this determined ACTUALgray scale value is compared with a predefined target gray scale value.In a certain range of the gray scale values, the better the connectionis between the functional layers 7, the higher the determined ACTUALgray scale value will be which is determined by the data processingdevice 13 for the generated image. This makes use of the fact that thebetter the adhesive connection is between the functional layers 7, thedarker the image will be and consequently the higher the gray scalevalue will be, until it finally reaches a maximum. If the gray scalevalue increases beyond that, the adhesive strength can decrease again.Thus, if a determined ACTUAL gray scale value is exactly at or above thepredetermined TARGET gray scale value, the connection between thefunctional layers 7 has been produced correctly. If, on the other hand,gray scale values which are below the TARGET gray scale value aredetermined in the electrode-separator assemblies to be monitored, thenthe connections between the functional layers 7 are incorrect and thecorresponding length of the electrode-separator assembly 3 is defectiveand should be disposed of as a reject. The result of this comparisonbetween the determined ACTUAL gray scale value and the specified TARGETgray scale value is then output as an evaluation result. This can takeplace, for example, by means of a second signal line 14 to a PLCcontroller 15 and further via a third signal line 16 to a server 17. Theserver 17 can either be operated locally or can be designed as aso-called cloud solution.

With the device described, the functional layers or cell components,such as anodes, separator layers or cathodes, can be firmly connected toone another, and can be arranged so that they are positioned andoriented very precisely with respect to one another. A so-calledelectrode-separator assembly is created by the connection of thefunctional layers or cell components. This can be used in particularwith large-format battery cells. Such battery cells will be required inlarge numbers in the future, which is why the manufacture thereof athigh process speeds is of particular advantage in order to reduce costsand to achieve the required quality.

Furthermore, the performance values of battery cells that aremanufactured as suggested here can also be improved. This then alsoimproves the properties of the finished batteries in which battery cellswith such electrode-separator assemblies are included.

The sometimes very sensitive materials that have to be processed in theproduction of battery cells can be processed safely and quickly with thepresent method and the present device, and at the same time theundesirable manufacture of large quantities of defectiveelectrode-separator assemblies is avoided. For this purpose, the in-lineinspection that is provided is used to determine the quality of theconnection between the functional layers. In contrast to the methodspreviously known in the prior art, the ongoing manufacturing process nolonger has to be analyzed using individual samples, but continuousanalysis can take place in real time. Thus, possible deficits in theproduction process are discovered immediately and not only after theproduct has been completed. This can reduce the production costs and cansignificantly improve the efficiency of the production process. Use ismade of the knowledge that investigations have recognized a correlationbetween the surface brightness or the gray scale value of the laminatedelectrode-separator assemblies and the lamination parameters such aspressure and temperature used in the manufacturing process. As thecompression rate increases, the gray scale value also increases. Thus,samples of electrode-separator assemblies, which may also be designatedsimply as laminates and are exposed to higher compression, appear“darker” because, for example, the surface of the cathode shows throughthe separator layer to a greater extent. The same applies to changes intemperatures. Here, too, the gray scale value is reduced by increasingthe temperature during the lamination process. Since the two parametersof pressure and temperature are also correlated with the adhesivestrength of the laminated electrode-separator assembly, the quality ofthis adhesive strength can also be assessed. It is thus possible todetermine the adhesive strength directly by determining the gray scalevalue of the electrode-separator assembly. In this way, directly afterthe lamination process, a conclusion can be reached about the quality ofthe intermediate product in the form of the relevant inspectedelectrode-separator assembly without having to carry out a destructivetest procedure. In addition, the device or the data processing devicecan be designed with an optical detection of flaws in order to controlthe lamination in-line, i.e. in the ongoing manufacturing process. Inthis way, both large-area unlaminated flaws and local foreign particlescan be detected, which enables complete quality control of theelectrode-separator assembly.

FIG. 2 shows the steps of the method from the lamination of theelectrode. Then the laminated electrode is first fed to the measuringsystem. Optimal illumination is provided there by a lighting system inorder then to generate a measurement result with a camera system in thenext step. After this, the measurement result in the form of an imagefor image processing is fed to a data processing device, where theACTUAL gray scale value is determined. The image can be a color image ora gray scale image. This takes place by means of a gray scale histogramfor the defined area integral. In a further step, an average ACTUAL grayscale value is formed from the gray scale histogram, and is thencompared in a next step with a predetermined TARGET gray scale value. Inthe last step, an evaluation result is generated and output from thecomparison of the ACTUAL gray scale value with the SET gray scale value.For this purpose, the output can take place in a visual, optical,haptic, acoustic or other form which is suitable for conveying theevaluation result to a human user. In a particularly simple embodiment,the evaluation result can be output as a binary value, such as good/bad,yes/no, and thus can inform the user whether or not theelectrode-separator assembly meets the requirements. With another formof output of the evaluation result, this can take place in the form ofsignals which are intended for further processing in a data processingdevice.

In FIG. 3, the relationship between the gray scale value and theadhesive strength between the functional layers 7 is shown qualitativelyusing a specific example. It can be clearly seen in this figure thatfrom a gray scale value G1 of approximately 175 [N] the adhesivestrength already reaches a very high value, reaching approximately 90%of a maximum value which the adhesive strength reaches at the gray scalevalue G2. Thus, for example, the value 175 can serve as a target valueabove which a sufficiently good connection exists between the functionallayers 7. As a result, all electrode-separator assemblies 3 with a grayscale value that is greater than this target value G1 of 175 [N] andless than the target value G2 of 100 [N] can be identified as correctlymanufactured parts and can be further processed. However, parts thathave a gray scale value that is below this target value G1 or above thetarget value G2 can be identified immediately as defective parts and canbe removed from the production process. Alternatively, starting from thetarget value G2 which corresponds to the maximum adhesive strength, arange can also be selected in which the adhesive strength is at least80%, preferably at least 90% of the maximum adhesive strength. For thispurpose, the range could be selected, for example, such that it extendsfrom the lower target value G1 located on the left side of G2 to anupper target value G3 located on the right side of G2 (not shown in thefigure). If the determined actual value of the gray scale value is inthis range, it is ensured that the adhesive strength is at least 80% andpreferably at least 90% of the maximum adhesive strength.

Finally, FIG. 4 shows a motor vehicle 18 which has an electric drive.The electric drive consists of an electric motor 19 which is operated bymeans of electrical energy provided by a battery 20. The battery 20 inturn has a large number of battery cells 21. The energy output of thebattery 20 to the electric motor 19 is controlled by means of a controldevice 22. The battery cells 21 arranged in the battery 20 are equippedwith electrode-separator assemblies 3 according to the present inventionand thus have the advantages that the functional layers 7 are connectedparticularly reliably, the battery 20 has improved performance and theproduction costs are reduced.

LIST OF REFERENCE SIGNS

-   1 device-   2 feed device-   3 electrode-separator assembly-   4 electrode-   5 separator layers-   6 active material layers-   7 functional layers-   8 housing-   9 lighting system-   10 surface-   11 camera system-   12 signal line-   13 electronic data processing device-   14 second signal line-   15 PLC control-   16 third signal line-   17 server-   18 motor vehicle-   19 electric motor-   20 battery-   21 battery cell-   22 control device

1. A method for inspection of a multilayer electrode-separator assemblyfor a battery cell, comprising at least the following steps: a) joiningtogether at least two functional layers; b) connecting the functionallayers (to form a multilayer electrode-separator assembly; c) detectingat least part of a surface of the electrode-separator assembly by meansof a detection device for generating a measurement result; d) evaluatingthe generated measurement result and generating an evaluation result;and e) outputting the evaluation result.
 2. The method for inspection ofan electrode-separator assembly for a battery cell according to claim 1,wherein the step of joining together comprises joining together at leastone electrode with an active material layer and at least one separatorlayer.
 3. The method for inspection of an electrode-separator assemblyfor a battery cell according to claim 1, wherein the functional layersare connected to one another by means of a lamination process, adhesiveprocess or welding process.
 4. The method for inspection of anelectrode-separator assembly for a battery cell according to claim 1,wherein steps a) to e) are carried out one after the other in acontinuous process (in-line).
 5. The method for inspection of anelectrode-separator assembly for a battery cell according to claim 1,wherein the step of detecting at least part of a surface of theelectrode-separator assembly surface is carried out using an opticalcamera system.
 6. The method for inspection of an electrode-separatorassembly for a battery cell according to claim 1, wherein the step ofevaluating the generated measurement result is carried out using anelectronic data processing system configured for image processing. 7.The method for inspection of an electrode-separator assembly for abattery cell according to claim 1, wherein, the step of evaluating thegenerated measurement result comprises: determining an associated ACTUALcharacteristic value, comparing the determined ACTUAL characteristicvalue with a predetermined TARGET characteristic value, and determiningthe evaluation result by comparing the ACTUAL characteristic value andthe TARGET characteristic value.
 8. The method for inspection of anelectrode-separator assembly for a battery cell according to claim 7,wherein the associated ACTUAL characteristic value is a gray scalevalue.
 9. The method for inspection of an electrode-separator assemblyfor a battery cell according to claim 1, wherein step c) is carried outunder constant and defined lighting conditions.
 10. A device forinspection of a multilayer electrode-separator assembly for a batterycell, with a feed device for an electrode sheet, characterized in that adetection device for detecting at least part of the surface of theelectrode-separator assembly is provided, which generates a measurementresult corresponding to the detection and which has an evaluation devicefor evaluating the measurement result, which device outputs anevaluation result after the evaluation has taken place.
 11. A devicewith at least one detection device and means which are suitable forcarrying out steps a) to d) according to claim
 1. 12. A battery cell(21), comprising: at least two electrodes which are separated by atleast one electrode-separator assembly, wherein a firstelectrode-separator assembly of a first pair of electrodes is separatedfrom a second electrode-separator assembly of a second pair ofelectrodes by at least one separator layer, wherein said at least oneseparator layer has an at least two-layer structure and is manufacturedusing the method according to claim
 1. 13. The battery cell according toclaim 12, wherein the battery cell is a lithium-ion cell.